Antihalation backing for photographic film



G. F. NADEAU El AL 2,131,747 ANTIHALAT ION BACKING F'OR PHOTOGRAPHIC FILM Fil'ed Oct. 13, 1957 13 JENS/T/Vf EMULSION SUPPORT Lkmsmmmxmxmxfi 12.

SENSITIVE EMULSION LAYERS SUPPORT 10 POLYV/NYL PHTHALATE LAYER 1 1g CONTAINING DYE 13 I 5EN5/T/VE EMuL5/0/v 5UPPOR T POM VINYL PHTHALATE LAYER CONTAINING DYE 15' PROTECTIVE COAT/N6 Gale F Nadeau INVENTORS W 11. KW

BY 69. Jim/{M ATTORNEY 8 Patented Oct. 4, 1938 UNITED STATES PATENT OFFICE ANTIHALATION BACKING Fon rno'ro- GRAPHIC FILM Jersey Application October 13, 1937, Serial No. 168,786

Claims.

This invention relates to photographic film and more particularly to a backing for such film for x the purpose of reducing the halation of reflection of light from the support to the sensitive 6 layer of the film.

The problem of halation is well knownin the photographic art and various means for overcoming it have been devised. Halation occurs in a photographic film or plate when a light-sensitive l0 film or plate is exposed to a well-lighted subject and the surface of the film or plate support does not containa light-absorbing material. Light rays are reflected onto the sensitive material from the support and produce a spreading of the image which is known as halation. This undesirable effect can be overcome by placing a light-absorbing material on one of the surfaces of the support, usually on the rear surface, so that the rays which would otherwise be reflected onto the sensitive layer are thereby absorbed.

As applied to photographic films, the antihalation layer is usually a separate layer of gelatin or other colloidal material containing a coloring material. It is desirable to color this gelatin layer with a dye which is immediately decolorized in the developer solution, but dyes of this character are rare and it has, therefore, been proposed to use as the carrier for the dye a water-susceptible material which is washed away during the proc- 80 essing of the film. A water-susceptible or watersoluble layer of this type carries the dye with it when washed away and, therefore, completely removes the dye from the film. A finished film is, therefore, obtained which is free from any residual stain from the antihalation dye since the dye is completely removed and since the dye has not been permitted to reach the surface of the film.

Many of the materials, which have been sug- 4o gested for use as water-susceptible or water-soluble layers for carrying the anti-halation dye, are lacking in desirable properties. Some of them adversely affect the photographic emulsion, while others do not possess suificient solubility in suitable solvents to permit their application to the film support. Other materials are soluble only in solvents which penetrate the film support to such an extent that an appreciable proportion of the antihalation dye is carried into the support and thus produces a permanent stain in it. Other materials are not sufliciently soluble in water or in the developing solutions to permit their ready removal from the film.

It is, therefore, an object of the present invention to provide an antihalation layer for photoraphic films or plates which comprises a readily removable material which may be colored or coated with an antihalation dye. A further object is to provide an antihalation material of this type which may be easily applied from suitable sol- -vents which do not penetrate the film support to any great extent. A still further object is to provide an antihalation backing of this type which is readily removed in the developing solution in which the film is processed. Other objects will appear from the following description of our invention.

These objects are accomplished by the use of polyvinyl phthalate as an antihalation backing material.

In the accompanying drawing Fig. 1 is an enlarged sectional view of a film having a sensitive layer coated with an antihalation backing of polyvinyl phthalate.

Fig. 2 is an enlarged sectional view of a threelayer film coated with a similar backing material, and

Fig. 3 is an enlarged sectional view of a film coated with a polyvinyl phthalate antihalation layer over which is a thin protective coating.

The material which I propose to use as an antihalation backing is an ester formed from polyvinyl alcohol and phthalic anhydride the material formed in this way being known as polyvinyl phthalate and containing a free carboxylic acid group. Polyvinyl phthalate is readily soluble in water containing traces of alkali and does not require a soaking or swelling as many so-called water-soluble resins do. It is soluble in a number of organic solvents which do not penetrate cellulosic film support, such as ethyl alcohol. It is compatible with gelatin and does not adversely affect photographic emulsions.

In accordance with my invention a 3 to 8% solution of polyvinyl phthalate in an equal mixture of methyl alcohol and butyl acetate is prepared. The amount of polyvinyl phthalate in the solution will depend on the speed at which it is coated on the cellulosic support, the thickness of the resin layer desired, and the amount of dye to be applied for antihalation protection. The amount of resin may vary above or below these limits but for ordinary purposes the range stated has been found to be satisfactory. The solution from which the resin is coated may have the following composition:

Butyl acetate 47.5

After the resin layer has been allowed to dry, a solution of an antihalation dye is applied to it, the dye being dissolved in suitable solvents in concentrations sufficient to obtain the desired color density. The following solution may be used:

Grams Alkali Bue B 4 Methyl alcohol 90 Water 6 Alkali Blue B has Color Index No. 704. Other suitable dyes may be used, it being generally desirable that they are alcohol-soluble as well as water-soluble and can, therefore, be applied to the polyvinyl phthalate from organic solvents in the conventional manner. For example, a solution of 5 grams of Acid Blue (Color Index No. 707) in 95 grams of methyl alcohol is also suitable.

After the dye solution has dried, a coating of suitable protective material may be applied over the antihalation layer, for the purpose of preventing transfer and scraping of the backing from the film by abrasive agents as in the further coating of the emulsion layers on the film or in passage of the film through the camera gate. A coating of carnauba wax is suitable for this pur pose. This coating, however, is not essential.

Our invention will now be described by particular reference to the accompanying drawing.

As shown in Fig. 1 of the drawing a support IU of any suitable material, such as cellulose nitrate, cellulose acetate, cellulose acetate propionate or cellulose acetate butyrate is coated with an antihalation layer ll of polyvinyl'phthalate and is then coated with an antihalation dye l2. A sensitive emulsion I3 is coated on the opposite side of the support 10. The dye l2 may also be mixed with the resin comprising the layer ii prior to coating in which case it will be substantially uniformly dispersed throughout the resin layer. As a further alternative the dye layer l2 may be such that it does not penetrate the polyvinyl phthalate layer II and, therefore, forms a separate layer coated on the surface of the polyvinyl phthalate layer.

In Fig. 2 we have shown a modification in which the support i is coated with the polyvinyl phthalate layer il containing the dye l2 as described above," but instead of a single emulsion layer the opposite side of the support contains three emulsion layers l4, l and I6 sensitive to different spectral regions for use in multi-color photography. The layers I4, l5 and I6 may have inert gelatin layers ll coated between them. In this type of filmit is sometimes desirable to expose either or both of the layers l5 and I5 through the support during processing and for this purpose it is essential that the antihalation backing, or at least the dye of the backing, be removed during initial stages of the processing. Since the polyvinyl phthalate used, according to our invention, is readily removed in developing solutions it is well adapted for use on films of this type, being removed in the first developing bath in which the film is treated.

A further modification of our invention is shown in Fig. 3 in which the support In is coated with the polyvinyl phthalate layer II and dye l2, the sensitive layer. i3 being coated on the opposite side of the support in the conventional manner. In this case a protective coating 18 of carnauba wax or other suitable material is coated over the polyvinyl phthalate layer II to protect it from abrasion during further treatment of the film.

The polyvinyl phthalate layer used according to our invention acts as a mordant for the dye, inhibits its water-solubility, and thus prevents the transfer of the dye to the emulsion when the film is exposed to high relative humidities. It also tends to prevent staining of the gelatin by those water-soluble dyes which are not decolorized or destroyed in the developing bath. The film containing the backing layer described may be treated in weakly alkaline developers, for example, as weakly alkaline as pH 7.5, and it is found that the antihalation layer will be bleached in a short time since the fugitive dye is destroyed by the alkali and the polyvinyl phthalate is rapidly dissolved and washed away without agitation. The whole process requires less than one minute.

The polyvinyl phthalate may be dissolved in solvents other than butyl acetate and methyl alcohol, such as ethyl alcohol, butyl carbitol, methyl Cellosolve (ethylene glycol monomethyl ether) and others. Esters other than the phthalic acid esters of polyvinyl alcohol may also be used. For example, esters of succinic acid, maleic acid and other dibasic acids are considered suitable as long as the resulting ester has a free carboxylic acid group.

In addition to its use as an antihalation layer the polyvinyl phthalate coatings may also be used as an anti-static backing or as a protective coating over the emulsion layer or on the opposite side of the photographic support. Other modifications of our invention may also be made within the scope of the appended claims.

What we claim is:

1. A photographic element comprising a lighttransmitting support having thereon an antihalation layer of polyvinyl phthalate and a dye.

2. A photographic element comprising a lighttransmitting support having thereon an antihalation layer of polyvinyl phthalate and a watersoluble and alcohol-soluble dye.

3. A photographic element comprising a lighttransmitting support having thereon an antihalation layer of polyvinyl phthalate and a blue water soluble and alcohol-soluble dye.

4. A light-sensitive photographic element comprising a light-transmitting support having on one side thereof a sensitive photographic layer and on the opposite side an antihalation layer of polyvinyl phthalate and a dye.

5. A light-sensitive photographic element comprising a light-transmitting support having on one side thereof a sensitive photographic layer and on the opposite side an antihalation layer of polyvinyl phthalate and a water-soluble and alcohol-soluble dye.

6. A light-sensitive photographic element comprising a light-transmitting support having on one side thereof a sensitive photographic layer and on the opposite side an antihalation layer of polyvinyl phthalate and a water-soluble dye of a color to which the emulsion is sensitive.

7. A light-sensitive photographic element comprising a light-transmitting support having on one side thereof a sensitive photographic layer and on the opposite side an antihalation layer of polyvinyl phthalate and a blue, water-soluble and alcohol-soluble dye.

8. A light-sensitive photographic element com prising a light-transmitting cellulosic support having on one side thereof a light-sensitive photographic layer and on the opposite side an antihalation layer of polyvinyl phthalate and a blue, water-soluble and alcohol-soluble dye.

9. A light-sensitive photographic element comprising a light-transmitting cellulosic support soluble and alcohol-soluble dye, the combined layers being removable in an alkaline photographic developer and serving to protect the film from halation.

GALE F. NADEAU. CLEMENS B. STARCK. 

